Natural furocoumarins, some of which are carcinogenic, are widespread components of the diet which are frequently consumed. Because of the paucity of samples, the wide scatter of analytical values, and other limitations in the data, only broad conclusions can be drawn. Most of the exposure is from limes, with smaller amounts coming from other citrus and umbelliferous food plants. The per capita exposure is estimated to be 1.3 mg per day. Exposure can be reduced through controlling stress in growing plants and stored food products. Because furocoumarins are one class of a large group of chemicals in a defensive system essential to plant survival, their total eradication is not possible. Further research is needed to assess their health risk.